Tube Temperature Thermocouples

Obtaining accurate temperatures of refinery heater tubes is difficult because many factors are involved. The point of measurement on a heater tube is surrounded by high temperature gases and flames. These gases are commonly as much as 600 – 800°F hotter than the heater tube at point of measurement. The gases are also corrosive to thermocouple materials. Heat transfer along the length of the thermocouple assembly to its point of attachment on the heater tube tends to cause the thermocouple to be responsive to the higher gas temperatures rather than the desired tube wall temperature.

Many attempts to monitor tube wall temperature with accuracy and reliability have failed because either the attachment of the element to the tube was inadequate or the shielding to prevent direct flame impingement at the point of attachment was too extensive.

When the conventional “Pad” thermocouple is welded to a tube surface, a void space may occur between the underside of the pad and the tube surface. This void space impedes heat transfer from the pad to the cooler heater tube wall. The result is that heat energy from flame impingement and furnace gases flow to the pad edges and through the securing welds to the tube wall. This indirect flow path retards the absorption rate of the tube surface beneath the pad and the thermocouple is responsive to pad temperature which is considerably higher than tube wall temperature.

The “Tube Temp” thermocouple is designed to be responsive to tube wall temperature by placing the thermojuction in fused contact with the tube wall and by providing a direct and totally metallic heat transfer path from the sheath to the tube wall.

When you specify “Tube Temp” thermocouples, you are specifying an unsurpassed technology currently in use around the world. You will also receive unparalleled service and support from Thermo-Couple Products. With quality programs in place to meet and exceed the requirements of ISO 9001:2000, you can be sure that you are buying the best when you ask for Thermo-Couple Product’s “Tube Temp” thermocouple.

Pad Type 1700 is a Low Cost Alternative to “Tube Temp” Thermocouple Pad is Slotted for Higher Accuracy Used Where Severe Service Atmospheric Conditions are Not a Major Concern Suitable for Tight Space Limitations Can be Field Formed

Pad Type 1710 is a Lower Cost Alternative to “Tube Temp” Thermocouple Thermocouple is Welded on Top of Pad Used Where Severe Service Atmospheric Conditions are Not a Major Concern Suitable for Tight Space Limitations Can be Field Formed